Circuit breaker



July 3, 1928. 1,676,143

M. s. HOBAN C IRCUIT BREAKER Filed Sept. 20, 1926 Patented July 3, 1928.

UNITED ,STA

MARK STA'VELEY HOIBAN, OF LONDON, ENGLAND.

CIRCUIT Application filed September 20, 1926, Serial No This inventionrelates to a circuit breaker or switch for use in electric circuits andwhich may be hand operated or arranged to operate automatically on thepassage of an excess current.

One form of circuit breaker according to the invention and for use in adistribution board for an electrical installation in place of the usualfusible cut out will be described with reference to the accompanyingdrawings wherein Fig. 1 shows the circuit breaker with the cover andactuating lever removed;

Fig. 2 shows the member of insulating material;

Fig. 3 is a plan of the operating mocha nism; and

Fig. 4 an elevation of the circuit breaker with the cover in position.

1 is a body part of insulating material which is recessed at 2 and hascontact blades 3. 1 similar to those of an ordinary fuse block, onemounted at each end. To the blade 3 is connected a conducting strip 5which extends into the recess 2, and to the blade 4 a conducting strip 6which extends over the recess 2. A V-shaped bi-metallic strip isdisposed in the recess 2 and is secured at the end of one arm 7 to theend of the conducting strip 5 and to the body part 1. The end of theother arm 8 is secured to one end of a conducting strip 9 also in therecess 2 and to the body part 1. The conducting strip 9 is so disposedthat its other end lies under the end of the conducting strip 6. On apin 10 extending from the body part 1 and in the recess 2 is rotatablymounted a sector-shaped member of insulating material 11. Towards onecorner the member 11 car ries a stud 12 of conducting material, theposition being such that at one end of the movement of the member 11 thesaid stud is disposed between and engages the conducting strips 6 and 9to complete an electrical connection between the two. A flat spring arm13 is rotatably mounted at one end on the pin 10 and extends along oneedge of the member 11. Towards its other end it carries a pin 14 whichprojects through a hole in the member 11 and engages a sto 15 carried onan actuating lever 16 which 1s pivotally mounted on the pin 10 withoutthe cover 19 for the body part 1 (see Fig. 4). A spring 17, which isconnected at one end to the member 11 and is anchored at the other endto a stationary part of the circuit breaker, acts BREAKER.

. 136,484, and in Great Britain October 12, 1825.

to urge the member 11 in a clockwise direction. The base 18 of theV-shaped bi-metallic strip 7, 8 is bent over to embrace the end of thespring arm 13.

The bi-metallic strip is of well known form consisting of strips ofdifferent metals such as brass and steel brazed or otherwise joinedthroughout their length so that when heated the strip bends, due to thedifferent coeflicients of expansion of the two metals.

When the circuit breaker is connected in an electrical circuit and theparts are in the position shown in Fig. 1, current flows from thecontact 3 through the conducting strip 5, the bi-metallic strip 7, 8,the conducting strips 9 and 6 to the contact 1. Should the currentexceed a predetermined value, the bi-metallic strip will heat and bendtowards the body part 1, whereby the bent base 18 will engage the end ofthe spring arm 13 and withdraw the pin 14 from engagement with the stop15. The member 11 is then free to rotate in a clockwise direction underthe action of the spring 17, whereby the circuit is rapidly broken andan arc is prevented by the insertion of the member 11 between theconducting strips 9 and 6.

The circuit breaker is replaced or the circuit remade by rotating theoperating lever lti first in a clockwise direction until the pm 14 againcomes under the stop 15, and then in an anti-clockwise direction so thatthe position shown in Fig. 1 is restored. If the abnormal conditions inthe electric circuit are still maintained, the bi-metallic strip will beimmediately heated and the circuit broken, even though the operatinglever 16 be held in position.

The construction of the parts is such as to limit the travel of theoperating lever 16 and of the member 11.

It will be understood that various modifications may be made in the formof the invention illustrated in the drawings. Thus the insulatingmaterial 11 may be mounted to move in a straight line and may be ofother than sector shape. It may be necessary to deal with currents whichare much larger or much smaller than those normally used in electriclighting circuits, in which case a portion only of the total currentwill be passed through the bi-metallic strip or the strip will be heatedby passing the current through a separate heating element. Similarly themovement of the plece of insulating material may be brought about byducting stud and movable in relation to said contacts to bring the studinto engagement therewith or to move ittherefrom, spring means to movesaid member, a detent to holdup said movement, and a V-shaped bimetallicstrip member electrically connected in the circuit of the pair ofcontacts and bent at its apex to co-operate with the detent and releasethe movable member on the strip becoming heated.

2. A circuit breaker for an electric circuit comprising apair ofcontacts, a pivotally mounted member of insulating material carrying aconducting stud and movable betweensaid contacts to bring the stud intoengagement with the contacts and to move it fromthe cont-acts, springmeans to move the member, a spring arm mounted at one end on the pivotand carr ing a in at the other end which engages t e mem er ofinsulating material, a movable arm, a stop mounted thereon and engagingthe pin, a V- shaped bi-metallic strip member electrically connected inthe circuit of the pair of contacts with its base bent over to embracethe end of the spring arm, and which on the strip being heated willengage the spring arm and remove the pin from engagement with the stop.

Dated this 2nd day of September, 1926. MARK STAVELEY HOBAN.

